Quick couplings, including coaxial quick couplings, are widely used to connect and disconnect hydraulic components in numerous applications. For example, several such applications involve hydraulic circuits in which one hydraulic hose receives supply or higher pressure hydraulic fluid from a pressure source such as a hydraulic pump and conveys the supply pressure hydraulic fluid from the pump to a tool or equipment that uses the supply pressure hydraulic fluid to perform work. A second hydraulic hose, which may be separate from the first hose or may be coaxially arranged about the first hose to provide a coaxial hose arrangement, receives return or lower pressure hydraulic fluid from the equipment and conveys the return pressure hydraulic fluid from the equipment to a fluid reservoir that is connected back to the hydraulic pump. In these described exemplary applications, a coaxial quick coupling or other type of quick coupling may be used to connect the hoses to the equipment, and/or to connect the hoses to the pump, and/or to connect hoses to one another in order to extend the distance between the pump and the equipment.
In these examples involving coaxial quick couplings, the coaxial quick coupling includes first and second coupling members or coupling halves that are quickly connected to and disconnected from one another. Each of the coupling halves includes a supply pressure passage that conveys higher pressure fluid from the pump to the equipment and a return pressure passage that conveys lower pressure fluid from the equipment back to the pump. Valves are provided that close to prevent flow or leakage from the passages when the coupling members are disconnected from one another. The valves open to allow fluid flow between the supply passages of the first and second coupling halves, and between the return passages of the first and second coupling halves, when the coupling halves are connected to one another.
U.S. Pat. Nos. 7,147,003 and 7,584,764 to Ojars Maldavs (“Maldavs patents”) disclose and explain the operation and method of a coaxial quick coupling (“Maldavs coupling”) of the above described general type. The Maldavs coupling today is widely and successfully used in emergency applications in which emergency rescue equipment is connected by hydraulic hose to a hydraulic pump. In these applications, the hydraulic pump may be located at or near a rescue vehicle that has an engine to power the hydraulic pump. The rescue equipment may be used at a location remote from the hydraulic pump such as, for example, at the location of an industrial or motor vehicle or other accident. The hydraulic hose extends between and carries the hydraulic fluid between the hydraulic pump and the remote rescue equipment.
The Maldavs coupling facilitates connecting the coupling halves when the hydraulic pump is running and higher pressure hydraulic fluid is flowing through the hose from the pump to one of the coupling halves and lower pressure hydraulic fluid is returning from the one coupling half back to the pump. The forces created by fluid pressure acting against various components of the one coupling half must be manually pushed against and overcome by the operator during connecting of the coupling halves to open the valves in the one coupling half. The lower return fluid pressure is utilized in the Maldavs coupling to reduce any fluid pressure acting against these various components of the one coupling half during connecting. Because the return fluid pressure is low relative to the supply fluid pressure from the pump, the forces created by the return fluid pressure acting against the mentioned components is relatively low so that the connecting force is relatively low even when the hydraulic pump is running and hydraulic fluid is flowing through the hose from and back to the pump.
In some applications, it may be desirable to increase flow rates of the hydraulic fluid in order, for example, to accommodate use of larger rescue equipment. Also, in some applications it may be desirable to increase the length of the hose, including by connecting sections of hose together, in order to permit use of rescue equipment at a greater distance from the hydraulic pump. Further, it may be desirable to connect the coupling under cold weather conditions when the hydraulic fluid is relatively cold. When higher flow rates are desired or when longer hoses are desired or when low temperatures are encountered, the return pressure increases. The connecting forces in such applications are still reduced in the Maldavs coupling, but the higher return pressure increases the connecting forces above those in similar applications with lower fluid flow rates or shorter hoses or higher fluid temperatures. The present invention provides an improvement for the Maldavs coupling, and for other couplings including other coaxial and non-coaxial couplings, that addresses the technical problem of high connecting forces and reduces connecting forces and permits connecting when the pump is running under a wide variety of flow rates and hose lengths and fluid temperatures.